Abstract
Objective. To evaluate the percentage of elevated stimulated thyroglobulin (sTg) and persistent or recurrent disease (PRD) in patients with detectable basal Tg < 0.3 ng/mL. Methods. The sample consisted of 130 patients with papillary thyroid carcinoma (PTC) who were at low risk of PRD and who had neck ultrasound (US) without abnormalities, negative anti-Tg antibodies (TgAb), and detectable basal Tg < 0.3 ng/mL about 6 months after ablation. Results. sTg was <1 ng/mL in 88 patients (67.7%), between 1 and 2 ng/mL in 26 (20%), and ≥2 ng/mL in 16 (12.3%). Imaging methods revealed the absence of tumors in 16 patients with elevated sTg. During follow-up, Tg increased to 0.58 ng/mL in one patient and lymph node metastases were detected. Sixty-nine patients continued to have detectable Tg < 0.3 ng/mL and US revealed recurrence in only one patient. Sixty patients progressed to persistently undetectable Tg without apparent disease on US. Conclusions. In low-risk patients with PTC who have detectable basal Tg < 0.3 ng/mL after ablation, negative TgAb, and US, persistent disease is rare and eventual recurrences can be detected by basal Tg elevation and/or subsequent US assessments, with follow-up without sTg being an “alternative” to Tg stimulation.
Highlights
Stimulated thyroglobulin is not recommended for the follow-up of patients with papillary thyroid carcinoma (PTC) submitted only to thyroidectomy
The present study evaluated patients with PTC who met criteria (i) to (v) described above and had detectable basal Tg < 0.3 ng/mL about 6 months after ablation with 131I
International Journal of Endocrinology started to be used) and January 2013 who met the following criteria were selected: (a) diagnosis of PTC, (b) submitting to total thyroidectomy followed by ablation with 131I, with apparently complete tumor resection and RxWBS showing no uptake outside the thyroid bed, (c) low risk of persistent or recurrent disease (PRD), and (d) US without abnormalities, negative Tg antibodies (TgAb), and detectable basal Tg < 0.3 ng/mL about 6 months after initial therapy [5,6,7]
Summary
Stimulated thyroglobulin (sTg) is not recommended for the follow-up of patients with papillary thyroid carcinoma (PTC) submitted only to thyroidectomy (without radioiodine). In patients treated with 131I, sTg is not necessary if basal Tg is significantly elevated (traditionally > 1 ng/mL) or, at the other extreme, in patients with the following criteria: (i) apparently complete tumor resection, (ii) absence of uptake outside the thyroid bed on posttherapy whole-body scanning (RxWBS), (iii) low risk of persistent or recurrent disease (PRD), (iv) neck ultrasound (US) showing no tumor, (v) absence of interference of anti-Tg antibodies (TgAb), and (vi) basal Tg “undetectable” by a second-generation assay (functional sensitivity of approximately 0.1 ng/mL). The need for sTg is controversial in patients who meet criteria (i) to (v) but have slightly elevated basal Tg measured with a second-generation assay. Some information is important to define the need for sTg in these cases: (a) percentage of patients with elevated sTg, (b) rate of persistent disease (not detected by US), and (c) rate of tumor recurrence after initial assessment. The objectives were to determine the percentage of patients with elevated sTg, persistent disease on initial assessment, and recurrence during follow-up
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